The invention concerns a transmission device for transmitting electrical signals between a rotor and a stator, having an annular space formed by the rotor and stator, wherein the space receives at least one flat strip cable which extends between the rotor and the stator and which can be wound and unwound in the space, wherein at least one elastically resilient annular band is provided in the space to support the flat strip cable.
A transmission device of this type may be used e.g. in the steering column region of a vehicle, wherein the rotor is disposed on the steering wheel side and the stator is disposed on the chassis side. In modern vehicles, a plurality of functions are actuated via steering wheel switches. The inventive transmission device can transmit the electrical signals triggered by the switches to users or control devices on the chassis side, which do not follow the rotary motion of the steering wheel.
DE 43 29 820 A1 discloses a transmission device wherein the flat strip cables are guided in the space. The flat strip cable may be shortened due to the guidance, thereby still permitting a sufficiently high number of rotations of the rotor. The flat strip cable usually consists of a plurality of parallel conductors which are combined using a base insulation material. Rotation aids in the form of blind cables which are mounted to the rotor and to the stator are provided to prevent the flat strip cable from being clamped or from slacking and thereby folding when the rotor is turned. A transmitting device of this type has proven to be relatively unreliable. Use of blind cables as the rotation aid is relatively demanding, since the blind cables must be wound together with the flat strip cable transmitting the signals when mounting the transmission device. If several flat strip cables are used to transmit a plurality of electrical signals, support of the flat strip cables using the blind cables becomes more and more difficult.
DE 197 34 527 A1 discloses a transmission device of the above-mentioned type, wherein several annular bands are disposed in the space. The annular bands have a predetermined elasticity and are structured to deform under load between the outer periphery of e.g. the inner rotor and the inner periphery of e.g. the outer stator. The annular bands roll on the inner periphery of the rotor or stator during rotation of the rotor. The annular bands thereby load the flat band against the outer or inner periphery. Anti-contacting elements in the form of rollers or balls are used to prevent contact between two neighboring annular bands. The anti-contacting elements also rotate in the rolling direction of the annular bands when the rotor is turned. This conventional arrangement is disadvantageous in that it requires a large number of movable components which are driven by the rotary motion of the rotor, i.e. the annular bands and the anti-contacting elements. Rattling noises cannot be prevented, in particular, due to the anti-contacting elements. Rotation of the rotor is also impaired by the anti-contacting elements which also rotate and are subjected to a certain amount of friction and wear.
It is therefore the underlying purpose of the present invention to provide a transmission device of simple construction which still permits permanent and reliable winding and unwinding of at least one flat strip cable between the rotor and the stator. In particular, at least one elastically resilient annular band should be provided to support the flat strip cable. The transmission device should, however, have a minimum amount of moving components thereby still preventing the annular band from impairing the rotary motion of the rotor or the motion of the flat strip cable in the space.